The date of Jesus’ birth

It is now generally agreed among historians and scholars that Christ’s year of birth was not correctly calculated. This refers to an error made by the monk Dionysius Exiguus, who in the early sixth century was given by Rome the task of extending the chronological tables of the Easter date that had been prepared at the time of Bishop Cyril.

The monk took as his starting point the date of the Lord’s incarnation. Dionysius’ mistake lay in the fact that he calculated Jesus’ birth to have taken place after the death of Herod − in other words four to six years after the date in which it actually occurred − which would have corresponded to 748 years after the founding of Rome.

But according to Flavius Josephus, Herod the Great died after ruling 37 years, and given that he was enthroned in 40 BC the year of his death would have been 4 BC. This is also confirmed by an astronomical event that the historian recorded as having taken place prior to the death of the monarch, namely a lunar eclipse that would have occurred between the 11th and 12th of April in the year 4 BC.

Based on this information the death of Herod must have occurred in the year 4 BC, and Jesus could not have been born later than that year. On the other hand, in terms of the month and day of Jesus’ birth the traditional dates appear to be accurate. To analyze the situation one must take into account two sources: the Gospel of Luke and the solar calendar discovered at Qumran.

Luke tells us that the angel Gabriel announced to Zechariah that Elizabeth was pregnant at a time “when he was serving as priest in his division’s turn before God” (Luke 1:8). Using these elements it is possible to calculate the 24 divisions in which the sacerdotal families were divided and date this back to the division of Abijah, the eighth and the one to which the priest Zechariah belonged, and which carried out its service from the eighth to the fourteenth day of the third month, and from the twenty-fourth to the thirtieth day of the eighth month.

This latter period corresponds to the end of September, nine months before the twenty-fourth of June, the date of John the Baptist’s birth. Hence the announcement to the Virgin Mary “in the sixth month” (Luke 1:28) of Elizabeth’s pregnancy corresponds to the twenty-fifth of March, so that the date of 25 December for Jesus’ birth can be seen to be historically accurate.

Nonetheless, it is commonly claimed that the traditional date of Jesus’ birth was established by the Church in order to correspond to the pagan festival Dies natalis solis invicti which took place on the day of the winter solstice (21 December), presumably to serve as a substitute for the pagan ceremony and to assist the rapid spread of the Christian one.

But it is evident that such an important feast day could not have been established only for reasons of such supremacy and that the tradition must have had roots that were more historic and real. It is indeed the case that the transition from the pagan to the Christian holiday was a very easy one, in view of the biblical tradition that saw the Messiah as light and sun: “the sunrise shall visit us from on high” (Luke 1:78).